There seem to be two town portals bugs around.
First, the old one messing the minions up after returning to the map.
Second, if you use Town Portal before opening some chests can result in the chests only give few gold pieces and/or basic items instead of the better items and/or a bigger amount of gold. This issue seems not to happen every time. Somehow it seems to register the return as an already opened chest before even if this is not true.